1. Field of the invention
The present invention relates to a full-color plasma display panel, and more particularly, to a full-color plasma display panel with a high color temperature that is achieved by adjusting the coverage of the phosphor materials within the plasma display panel.
2. Description of the Prior Art
A full-color plasma display panel (PDP) is composed of hundreds of thousands of tiny discharge cells arranged in a matrix formation. When a voltage is induced in one of these discharge cells, it causes a gas in the cell to discharge and generate ultra-violet radiation. This ultra-violet radiation falls on different phosphor materials and causes them respectively to emit one of three primary colors of light, i.e., red, green, or blue. Generally, the color of the emitted light depends on the composition of the phosphor materials. If the phosphor material is made of (Y,Gd)BO3, and Eu is added as a luminescent agent, the phosphor material will emit red light. If the phosphor material is made of Zn2SO4, and Mn is added as a luminescent agent, the phosphor material will emit green light. If the phosphor material is made of BaMgAl14O23, and Eu is added as a luminescent agent, the phosphor material will emit blue light. However, this blue light suffers from color degradation at higher temperatures. In order to improve the luminescence of the PDP, the discharge space for blue light is enlarged to increase the coverage of the associated phosphor materials. In this manner, the proportion of emitted red light, green light, and blue light of the PDP can be adjusted so as to promote color temperatures in the range of 7000K to 11000K.
Please refer to FIG. 1. FIG. 1 is a schematic diagram of a full-color plasma display panel 10 according to the prior art. The prior art PDP 10 comprises a first substrate 12, a second substrate 14 positioned in parallel to the first substrate 12, a discharge gas filling the space between the first substrate 12 and the second substrate 14, and a plurality of first electrodes 18, second electrodes 20, and address electrodes 22. Each of the first electrodes 18 and the second electrodes 20 are. alternately positioned on the first substrate 12 in parallel to each other. Each of the address electrodes 22 is positioned on the second substrate 14 perpendicular to the first electrodes 18 and the second electrodes 20. Each of the first electrodes 18 and the second electrodes 20 comprises a support electrode 181, 201 made of ITO, and a complementary electrode 182, 202 made of Cr/Cu/Cr, a sandwiched structure with three metallic layers. The support electrode 181, 201 is transparent to most visible light, but has great electrical resistance. The complementary electrode 182, 202 has better conductivity and thus enhances the conductivity of the first electrodes 18 and the second electrodes 20.
The PDP 10 further comprises a dielectric layer 24 that covers the first substrate 12, a protective layer 26 covering the dielectric layer 24, a plurality of barrier ribs 28 positioned on the second substrate 14 in parallel to each other for isolating two adjacent address electrodes 22 and defining a plurality of line-shaped discharge spaces 30, and a phosphor layer 32 coating the surfaces of the second substrate 14 and the walls of the barrier ribs 28 that surround each discharge space. The phosphor layer 32 emits red light, green light or blue light. Each of the discharge spaces 30 comprises a plurality of unit display elements 34 arranged in matrix formation between the first substrate 12 and the second substrate 14. All of the discharge spaces 30 are divided into a plurality of discharge space groups. Each of the groups comprises a red discharge space 30R coated with a red phosphor layer 32R, a green discharge space 30G coated with a green phosphor layer 32G, and a blue discharge space 30B coated with a blue phosphor layer 32B. Consequently, a plurality of red unit display elements 34R are formed within the red discharge spaces 30R, a plurality of green unit display elements 34G are formed within the green discharge spaces 30G, and a plurality of blue unit display elements 34B are formed within the blue discharge spaces 30B. Generally, one red unit display element 34R, one green unit display element 34G, and one blue unit display element 34B form a pixel.
In order to improve the luminescence of blue light emitted from the PDP 10, the width of the red discharge space 30R is designed to be the narrowest. The width of the green discharge space 30G is designed to be 1.2 times as wide as the width of the red discharge space 30R. The width of the blue discharge space 30B is designed to be 1.6 times as wide as the width of the red discharge space 30R. Therefore, the red unit display element 34R has smallest space, and the blue unit display element 34B has the largest space. Hence, the coverage of the red phosphor layer 32R is the smallest, and the blue phosphor layer 32B has the largest coverage. Under these size ratios, the red, green and blue light will combine to form white light with a color temperature of about 11000K.
However, the widths of the different discharge spaces 30 are designed according to specific proportions. When the size of all of the discharge spaces 30 needs to be reduced to increase the resolution of the PDP 10, the width of the red discharge space 30R can become quite small. This not only increases the difficulty of manufacturing the barrier ribs 28 and the red phosphor layer 32R, but can also lead to contraposition when sealing the first substrate 12 to the second substrate 14. Furthermore, the red discharge space 30R with a much smaller width can easily cause the discharge gas to cross talk with the adjacent discharge spaces 30. This interference damages the electrical performance of the PDP 10.
It is therefore a primary objective of the present invention to provide a full-color PDP with a higher color temperature by adjusting the coverage of the phosphor layer, and thus avoid the above-mentioned problems of the prior art.
In a preferred embodiment, the present invention provides a plasma display panel that comprises a back substrate, a front substrate positioned on the back substrate, with a space between the facing surfaces of the front substrate and the back substrate. A plurality of barrier ribs are positioned in the space for defining a plurality of discharge space groups wherein each group comprises a first discharge space and a second discharge space. A first traverse rib is positioned in each first discharge space. A second traverse rib is positioned in each second discharge space wherein the transverse length of the second traverse rib is smaller than that of the first traverse rib. A first phosphor layer is coated on the surfaces of the back substrate, the first traverse ribs, and on the barrier ribs surrounding each first discharge space. A second phosphor layer is coated on the surfaces of the back substrate, the second traverse ribs, and on the barrier ribs surrounding each second discharge space. The coverage of the first phosphor layer is greater than that of the second phosphor layer. For a first discharge space and a second discharge space, a distance between the side of the first traverse rib and the center of the first discharge space is less than a distance between the side of the second traverse rib and the center of the second discharge space. Thus, the luminous intensity of the first phosphor layer is greater than that of the second phosphor layer.
It is an advantage of the present invention that the plurality of barrier ribs, cooperating with the traverse ribs of various size and placements, adjusts the coverage of the phosphor layers. This adjusts the coverage proportions of the phosphor layers coated within each discharge space to promote a color temperature of the PDP of up to 11000K.
These and other objectives of the present. invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment which is illustrated in the various figures and drawings.